Branched Aliphatic-Aromatic Polyester Blends

ABSTRACT

Compositions of PHAs with aromatic/aliphatic polyester are described and methods of making the same.

This application claims the benefit of U.S. Provisional Application No. 61/269,582, filed on Jun. 26, 2009. The entire teachings of the above application is incorporated herein by reference.

BACKGROUND

Biodegradable plastics are of increasing industrial interest as replacements or supplements for non-biodegradable plastics in a wide range of applications and in particular for packaging applications. One class of biodegradable polymers is the polyhydroxyalkanoates (PHAs), which are linear, aliphatic polyesters that can be produced by numerous microorganisms for use as intracellular storage material. Articles made from the polymers are generally recognized by soil microbes as a food source. There has therefore been a great deal of interest in the commercial development of these polymers, particularly for disposable consumer items. The polymers exhibit good biodegradability and useful physical properties.

In some applications, the rapid biodegradability of PHAs can be a problem, and thus a need exists to control the rate of biodegradation of PHAs.

SUMMARY OF THE INVENTION

Described herein are compositions of branched polymer compositions comprising polyhydroxyalkanoates (PHAs) and biodegradable aromatic/aliphatic polyesters, methods of making such composition, and articles and pellets formed from such blends. In particular embodiments, the aromatic/aliphatic polyester is a polybutylene adipate-terephthalate. The PHAs are reactive blended with a polybutylene adipate-terephthalate. In particular, when the polymers are melt-blended in the presence of an a branching agent, for example, organic peroxide, the resultant compositions display many unexpected synergies in melt rheology, thermal stability, processing and properties, such as film processing and film properties. In addition, the biodegradation kinetics of PHB copolymers can be slowed down by combining a polybutylene adipate-terephthalate into the composition. In certain aspects, the process of reactive blending (melt reacting) further includes the use of a reactive cross-linking agent resulting in improved properties. In one embodiment, the PHA and a polybutylene adipate-terephthalate is blended, i.e., to a homogeneous blend. In certain aspects, the polymers of the compositions are mixed together to form a blend.

Combining (e.g, mixing or blending) the polymer blends in the presence of a reactive branching agent, e.g., peroxide, provides the following benefits compared to combining the polymer blends without any reactive chemistry: (1) higher melt strength, (2) improved thermal stability and/or better melt capillary stability, resulting in a broader processing window for the overall composition, (3) synergistic film properties, e.g., film tear properties of the compositions are better than PHA or aromatic/aliphatic polyesters film by itself, (4) higher toughness for injection molded bars, and (5) lower flash during injection molding process.

In certain embodiments, reacting with a branching agent is performed in the presence of a co-agent (also referred to herein, as a “cross-linking agent), thereby forming a branched polymer blend. The conditions of the reaction are suitable for reacting the branching agent alone or with a cross-linking agent and a polymer blend. A “branched” polymer is a polymer with a branching of the polymer chain or cross-linking of two or more polymer chains.

The cross-linking agent when reacted, for example, at its epoxide group(s) or double bond(s), becomes bonded to another molecule, e.g., a polymer or branched polymer. As a consequence the multiple molecules become cross-linked through the reactive group on the cross-linking agent. An “epoxy functional compound” is a cross-linking agent comprising two or more epoxy functional groups.

In certain embodiments, the functional group of the cross-linking agent is an epoxy-functional compound, for example, an epoxy-functional styrene-acrylic polymer, an epoxy-functional acrylic copolymer, an epoxy-functional polyolefin copolymer, oligomers comprising glycidyl groups with epoxy functional side chains, an epoxy-functional poly(ethylene-glycidyl methacrylate-co-methacrylate), or an epoxidized oil, poly(ethylene-co-methacrylate-coglycidyl methacrylate, ethylene-n-butyl acrylate-glycidyl methacrylate or combinations thereof

In other embodiment, the cross-linking agent contains at least two reactive double bonds. These cross-linking agents include but is not limited to the following: diallyl phthalate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, diethylene glycol dimethacrylate, bis(2-methacryloxyethyl)phosphate, or combinations thereof.

In any of the compositions or methods disclosed herein, the biodegradable aromatic/aliphatic polyester can have a glass transition temperature (T_(g)) of about 0° C. or less, of about −10° C. or less, or of about −20° C. or less. The glass transition temperature is the temperature at which an amorphous solid, such as glass or a polymer, becomes brittle on cooling, or soft on heating. As the temperature of a polymer drops below its T_(g), it behaves in an increasingly brittle manner. As the temperature rises above the T_(g), the polymer becomes more rubber-like. In particular embodiments, the aromatic/aliphatic polyester is a polybutylene adipate-terephthalate.

In one embodiment, a method of preparing a branched polymer composition, is described comprising reacting a PHA and a polybutylene adipate-terephthalate with a branching agent, and forming a branched polymer composition comprising a branched PHA and a polybutylene adipate-terephthalate blend.

Additives may also be included in the compositions and methods of the inventions. In particular embodiments, a nucleating agent is added.

In still another embodiment, a method of preparing a film comprising a branched polymer composition is described. The method comprises reacting a PHA with a branching agent, reacting a polybutylene adipate-terephthalate with a branching agent, and forming a branched polybutylene adipate-terephthalate polymer composition. Then, the branched PHA composition is exposed to conditions that cause melting of the PHA, thereby forming a molten branched PHA composition. The branched polybutylene adipate-terephthalate composition then is exposed to conditions that cause melting of the polybutylene adipate-terephthalate thereby forming a molten branched a polybutylene adipate-terephthalate composition, co-extruding the molten PHA compositions and the molten a polybutylene adipate-terephthalate compositions to form a multi-layered film; thereby making a film comprising branched PHA and branched a polybutylene adipate-terephthalate layers.

In still another embodiment, a method is described of making an article comprising a branched PHA and branched polybutylene adipate-terephthalate composition comprising: melt-blending PHA and polybutylene adipate-terephthalate and a branching agent under conditions that cause melting and branching of the PHA polymer and the polybutylene adipate-terephthalate, thereby forming a molten branched polymer composition; and forming an article from the branched molten polymer composition; thereby making an article comprising branched polymer composition of branched PHA and branched polybutylene adipate-terephthalate.

In certain embodiments, a film is prepared by the methods described herein, the resultant film has greater tear resistance according to ASTM D1922-06, greater puncture resistance according to D1709-04, or greater tensile strength according to D882-02 than a corresponding PHA film made without aromatic/aliphatic polyester. In some aspects, the film possesses properties that are 25% greater, 50% greater or 75-100% greater. In certain aspects, the film is a blend of branched PHA and branched polybutylene adipate-terephthalate.

In related embodiments of the invention, compositions, articles and films comprising branched PHA and branched polybutylene adipate-terephthate are also disclosed.

DETAILED DESCRIPTION

The invention provides branched polymer compositions and methods of preparing branched polymers with improved mechanical and rheological properties. The polymer compositions comprise preparing branched PHA and branched polybutylene adipate-terephthalate. The use of cross-linking agents further improve the desired properties of the polymer composition over the starting compositions without the cross-linking agents and branching agents. In one aspect, the cross-linking agents comprise two or more reactive groups such as double bonds or epoxides. These cross-linking agents react with and become covalently bonded (connected) to the polymer. The connection of multiple chains through these cross-linking agents form a branched polymer. The branched polymer has increased melt strength over the melt strength of the starting polymer.

Increased melt strength is useful in that it allows the polymers to be formed under a broader temperature range when the polymer is processed. This property for broader processing temperatures is useful for various polymer applications, such as in the production of blown film (i.e., in preventing or reducing bubble collapse), or cast film extrusion, thermoformed articles (i.e., preventing or reducing sheet sag during thermoforming), profile extruded articles (i.e., preventing or reducing sag), non-woven fibers, monofilament, etc. The polymer's stability is effected at processing temperatures and can accordingly experience a drop in melt strength. This can cause difficulties in processing these polymers. Additionally, the improvement shown in films made from the methods and compositions described herein are greater tensile strength, tear resistance and greater puncture resistance.

The methods and branched compositions of the invention improve the melt strength of polymer compositions, a desirable property for many polymer product applications. Melt strength is a rheological property that can be measured a number of ways. One measure is G′. G′ is the polymer storage modulus measured at melt processing temperatures.

Physical properties and rheological properties of polymeric materials depend on the molecular weight and distribution of the polymer. “Molecular weight” is calculated in a number of different ways. Unless other wise indicated, “molecular weight” refers to weight average molecular weight.

“Number average molecular weight” (M_(n)) represents the arithmetic mean of the distribution, and is the sum of the products of the molecular weights of each fraction, multiplied by its mole fraction (ΣN_(i)M_(i)/ΣN_(i)).

“Weight average molecular weight” (M_(w)) is the sum of the products of the molecular weight of each fraction, multiplied by its weight fraction (ΣN_(i)M_(i) ²/ΣN_(i)M_(i)). M_(w) is generally greater than or equal to M_(n).

One way of increasing the melt strength is by branching the polymers (PHA, aromatic/aliphatic polyesters), and various methods for accomplishing this are described herein. Branching the PHA is a result of reacting the polymer with branching agents, for example, peroxides. Also, cross-linking agents, for example, reactive compounds (compounds with epoxy groups and compounds with reactive double bonds) that enhance or increase the branching of the polymer, can also be used.

Addition of other reactive polymeric compounds, such as reactive acrylics, can also be employed to the rate of branching architecture of the PHA. The use and selection of additives to these compositions result in improved properties. All of these methods are described herein.

Aromatic/Aliphatic Polyester

The biodegradable aromatic/aliphatic polyester is a co polymer of: i) at least one aliphatic dicarboxylic acid; and/or ii) at least one aromatic dicarboxylic acid; and iii) a dihydroxy compound, in certain embodiments, the aliphatic dicarboxylic acid is a C₂ to C₁₂ alicphatic dicarboxylic acid such as, succinic acid, glutaric acid, dimethyl glutaric acid, adipic acid, sebacic acid or azelaic acid. In certain embodiments, the aromatic dicarboxylic acid is terephthalic acid or naphthalene dicarboxylic acid. In the embodiments of the invention, the aromatic/aliphatic polyester is polybutylene adipate-terephthalate.

The polyesters can be made from fossil-based carbon sources i.e., a petroleum-based polymer, e.g., synthetic polyesters such as, but not limited to, synthetic polyesters, or portions of the polyester can be made from biomass or other renewable sources of carbon.

Aromatic polyesters, which are not biodegradable, are synthesized by the polycondensation of aliphatic diols and aromatic dicarboxylic acids. The aromatic ring is resistant to hydrolysis, preventing biodegradability. Polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) are formed by the polycondensation of aliphatic glycols and terephthalic acid. The biodegradability of aromatic polyesters can be modified by the addition of monomers that are not resistant to hydrolysis, aliphatic diol or diacid groups. The addition of such hydrolysis-sensitive monomers creates weak spots for hydrolysis to occur.

In the synthesis of polybutylene adipate terephthalate (PBAT), butanediol is the dial, and the acids are adipic and terephthalic acids. Commercial examples include e.g., ECOFLEX® (BASF), Eastar BIO® (Novamont). Ecoflex has a melt temperature (Tm) of about 110° C. to about 120° C., as measured by differential scanning calorimetry (DSC). In preferred embodiments, the biodegradable polymers described in U.S. Pat. Nos. 6,018,004; 6,114,042; 6,201,034; and 6,303,677, incorporated herein by reference, are used in the compositions and methods described herein,

Biodegradable polymers therefore include polyesters containing aliphatic components. Among the polyesters are ester polycondensates containing aliphatic constituents or poly(hydroxycarboxylic) acids. In certain embodiments, the ester polycondensates include diacids/diol aliphatic polyesters such as polybutylene succinate, polybutylene succinate co-adipate, aliphatic/aromatic polyesters such as terpolymers made of butylenes diol, adipic acid and terephtalic acid.

Examples of biodegradable aromatic/aliphatic polyesters therefore include, but are not limited to, various copolyesters of PBT with aliphatic diacids or diols incorporated into the polymer backbone to render the copolyesters biodegradable or compostable; and various aliphatic polyesters and copolyesters derived from dibasic acids, e.g., succinic acid, glutaric acid, adipic acid, sebacic acid, azealic acid, or their derivatives (e.g., alkyl esters, acid chlorides, or their anhydrides) and dihydroxy compounds (diols) such as C₂-C₆ alkanediols and C₅-C₁₀ cycloalkanediols, such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6 hexanediol. In other embodiments, the diol is 1,4 cyclohexanedimethanol. In preferred embodiments, the dihydroxy compound is ethylene glycol, or 1,4-butanediol. Biodegradable diols are preferred in certain embodiments.

The biodegradable aromatic/aliphatic polyester can be a co-polyester. It can also itself be a blend of such polyesters or co-polyesters. For example, the co-polyester is a co-polyester of polybutylene adipate-terephthalate and another polyester.

Branching can be introduced into the polybutylene adipate-terephthalate to produce “high melt strength” having desired processability properties. Branching introduces side chains attached to the molecular chain backbones. The branches can vary in length and number. Branching can be accomplished by various methods known in the art. In particular embodiments, branching is accomplished with peroxide. Branching can also be introduced in addition to the peroxide by the use of isocyanate compound, as described in U.S. Pat. No. 6,114,042, incorporated by reference, assigned to BASF.

Melt strength is a measure of the elongational viscosity of polymer melt. It represents the maximum tension that can be applied to the melt without rupture or tearing. Usually a capillary viscometer is used to extrude a polymer stand and the strand is pulled till rupture by a pair of rollers.

Polyhydroxyalkanoates (PHAS)

Polyhydroxyalkanoates are biological polyesters synthesized by a broad range of natural and genetically engineered bacteria as well as genetically engineered plant crops (Braunegg et al., (1998), J. Biotechnology 65:127-161; Madison and Huisman, 1999, Microbiology and Molecular Biology Reviews, 63:21-53; Poirier, 2002, Progress in Lipid Research 41:131-155). These polymers are biodegradable thermoplastic materials, produced from renewable resources, with the potential for use in a broad range of industrial applications (Williams & Peoples, CHEMTECH 26:38-44 (1996)).

Useful microbial strains for producing PHAs, include Alcaligenes eutrophus (renamed as Ralstonia eutropha), Alcaligenes latus, Azotobacter, Aeromonas, Comamonas, Pseudomonads, and genetically engineered organisms including genetically engineered microbes such as Pseudomonas, Ralstonia and Escherichia coli.

In general, a PHA is formed by enzymatic polymerization of one or more monomer units inside a living cell. Over 100 different types of monomers have been incorporated into the PHA polymers (Steinbüchel and Valentin, 1995, FEMS Microbiol. Lett. 128:219-228. Examples of monomer units incorporated in PHAs include 2-hydroxybutyrate, lactic acid, glycolic acid, 3-hydroxybutyrate (hereinafter referred to as 3HB), 3-hydroxypropionate (hereinafter referred to as 3HP), 3-hydroxyvalerate (hereinafter referred to as 3HV), 3-hydroxyhexanoate (hereinafter referred to as 3HH), 3-hydroxyheptanoate (hereinafter referred to as 3HHep), 3-hydroxyoctanoate (hereinafter referred to as 3HO), 3-hydroxynonanoate (hereinafter referred to as 3HN), 3-hydroxydecanoate (hereinafter referred to as 3HD), 3-hydroxydodecanoate (hereinafter referred to as 3HDd), 4-hydroxybutyrate (hereinafter referred to as 4HB), 4-hydroxyvalerate (hereinafter referred to as 4HV), 5-hydroxyvalerate (hereinafter referred to as 5HV), and 6-hydroxyhexanoate (hereinafter referred to as 6HH). 3-hydroxyacid monomers incorporated into PHAs are the (D) or (R) 3-hydroxyacid isomer with the exception of 3HP which does not have a chiral center.

In some embodiments, the PHA in the methods described herein is a homopolymer (where all monomer units are the same). Examples of PHA homopolymers include poly 3-hydroxyalkanoates (e.g., poly 3-hydroxypropionate (hereinafter referred to as P3HP), poly 3-hydroxybutyrate (hereinafter referred to as P3HB) and poly 3-hydroxyvalerate), poly 4-hydroxyalkanoates (e.g., poly 4-hydroxybutyrate (hereinafter referred to as P4HB), or poly 4-hydroxyvalerate (hereinafter referred to as P4HV)) and poly 5-hydroxyalkanoates (e.g., poly 5-hydroxyvalerate (hereinafter referred to as P5HV)).

In certain embodiments, the starting PHA can be a copolymer (containing two or more different monomer units) in which the different monomers are randomly distributed in the polymer chain. Examples of PHA copolymers include poly 3-hydroxybutyrate-co-3-hydroxypropionate (hereinafter referred to as PHB3HP), poly 3-hydroxybutyrate-co-4-hydroxybutyrate (hereinafter referred to as P3HB4HB), poly 3-hydroxybutyrate-co-4-hydroxyvalerate (hereinafter referred to as PHB4HV), poly 3-hydroxybutyrate-co-3-hydroxyvalerate (hereinafter referred to as PHB3HV), poly 3-hydroxybutyrate-co-3-hydroxyhexanoate (hereinafter referred to as PHB3HH) and poly 3-hydroxybutyrate-co-5-hydroxyvalerate (hereinafter referred to as PHB5HV).

By selecting the monomer types and controlling the ratios of the monomer units in a given PHA copolymer a wide range of material properties can be achieved. Although examples of PHA copolymers having two different monomer units have been provided, the PHA can have more than two different monomer units (e.g., three different monomer units, four different monomer units, five different monomer units, six different monomer units). An example of a PHA having 4 different monomer units would be PHB-co-3HH-co-3HO-co-3HD or PHB-co-3-HO-co-3HD-co-3HDd (these types of PHA copolymers are hereinafter referred to as PHB3HX). Typically where the PHB3HX has 3 or more monomer units the 3HB monomer is at least 70% by weight of the total monomers, preferably 85% by weight of the total monomers, most preferably greater than 90% by weight of the total monomers for example 92%, 93%, 94%, 95%, 96% by weight of the copolymer and the HX comprises one or more monomers selected from 3HH, 3HO, 3HD, 3HDd.

The homopolymer (where all monomer units are identical) P3HB and 3-hydroxybutyrate copolymers (P3HB3HP, P3HB4HB, P3HB3HV, P3HB4HV, P3HB5HV, P3HB3HHP, hereinafter referred to as PHB copolymers) containing 3-hydroxybutyrate and at least one other monomer are of particular interest for commercial production and applications. It is useful to describe these copolymers by reference to their material properties as follows. Type 1 PHB copolymers typically have a glass transition temperature (Tg) in the range of 6° C. to −10° C., and a melting temperature T_(M) of between 80° C. to 180° C. Type 2 PHB copolymers typically have a Tg of −20° C. to −50° C. and Tm of 55° C. to 90° C. In particular embodiments, the Type 2 copolymer has a phase component with a T_(g) of −15° C. to −45° C. and no Tm.

Preferred Type 1 PHB copolymers have two monomer units have a majority of their monomer units being 3-hydroxybutyrate monomer by weight in the copolymer, for example, greater than 78% 3-hydroxybutyrate monomer. Preferred PHB copolymers for this invention are biologically produced from renewable resources and are selected from the following group of PHB copolymers:

PHB3HV is a Type 1 PHB copolymer where the 3HV content is in the range of 3% to 22% by weight of the polymer and preferably in the range of 4% to 15% by weight of the copolymer for example: 4% 3HV; 5% 3HV; 6% 3HV; 7% 3HV; 8% 3HV; 9% 3HV; 10% 3HV; 11% 3HV; 12% 3HV; 13% 3HV; 14% 3HV; 15% 3HV;

PHB3HP is a Type 1 PHB copolymer where the 3HP content is in the range of 3% to 15% by weight of the copolymer and preferably in the range of 4% to 15% by weight of the copolymer for example: 4% 3HP; 5% 3HP; 6% 3HP; 7% 3HP; 8% 3HP; 9% 3HP; 10% 3HP; 11% 3HP; 12% 3HP. 13% 3HP; 14% 3HP; 15% 3HP.

PHB4HB is a Type 1 PHB copolymer where the 4HB content is in the range of 3% to 15% by weight of the copolymer and preferably in the range of 4% to 15% by weight of the copolymer for example: 4% 4HB; 5% 4HB; 6% 4HB; 7% 4HB; 8% 4HB; 9% 4HB; 10% 4HB; 11% 4HB; 12% 4HB; 13% 4HB; 14% 4HB; 15% 4HB.

PHB4HV is a Type 1 PHB copolymer where the 4HV content is in the range of 3% to 15% by weight of the copolymer and preferably in the range of 4% to 15% by weight of the copolymer for example: 4% 4HV; 5% 4HV; 6% 4HV; 7% 4HV; 8% 4HV; 9% 4HV; 10% 4HV; 11% 4HV; 12% 4HV; 13% 4HV; 14% 4HV; 15% 4HV.

PHBSHV is a Type 1 PHB copolymer where the 5HV content is in the range of 3% to 15% by weight of the copolymer and preferably in the range of 4% to 15% by weight of the copolymer for example: 4% 5HV; 5% 5HV; 6% 5HV; 7% 5HV; 8% 5HY; 9% 5HV; 10% 5HV; 11% 5HV; 12% 5HV; 13% 5HV; 14% 5HV; 15% 5HV.

PHB3HH is a Type 1 PHB copolymer where the 3HH content is in the range of 3% to 15% by weight of the copolymer and preferably in the range of 4% to 15% by weight of the copolymer for example: 4% 3HH; 5% 3HH; 6% 3HH; 7% 3HH; 8% 3HH; 9% 3HH; 10% 3HH; 11% 3HH; 12% 3HH; 13% 3HH; 14% 3HH; 15% 3HH;

PHB3HX is a Type 1 PHB copolymer where the 3HX content is comprised of 2 or more monomers selected from 3HH, 3HO, 3HD and 3HDd and the 3HX content is in the range of 3% to 12% by weight of the copolymer and preferably in the range of 4% to 10% by weight of the copolymer for example: 4% 3HX; 5% 3HX; 6% 3HX; 7% 3HX; 8% 3HX; 9% 3HX; 10% 3HX by weight of the copolymer.

Type 2 PHB copolymers have a 3HB content of between 80% and 5% by weight of the copolymer, for example 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5% by weight of the copolymer.

PHB4HB is a Type 2 PHB copolymer where the 4HB content is in the range of 20% to 60% by weight of the copolymer and preferably in the range of 25% to 50% by weight of the copolymer for example: 25% 4HB; 30% 4HB; 35% 4HB; 40% 4HB; 45% 4HB; 50% 4HB by weight of the copolymer.

PHB5HV is a Type 2 PHB copolymer where the 5HV content is in the range of 20% to 60% by weight of the copolymer and preferably in the range of 25% to 50% by weight of the copolymer for example: 25% 5HV; 30% 5HV; 35% 5HV; 40% 5HV; 45% 5HV; 50% 5HV by weight of the copolymer.

PHB3HH is a Type 2 PHB copolymer where the 3HH is in the range of 35% to 95% by weight of the copolymer and preferably in the range of 40% to 80% by weight of the copolymer for example: 40% 3HH; 45% 3HH; 50% 3HH; 55% 3HH, 60% 3HH; 65% 3HH; 70% 3HH; 75% 3HH; 80% 3HH by weight of the copolymer.

PHB3HX is a Type 2 PHB copolymer where the 3HX content is comprised of 2 or more monomers selected from 3HH, 3HO, 3HD and 3HDd and the 3HX content is in the range of 30% to 95% by weight of the copolymer and preferably in the range of 35% to 90% by weight of the copolymer for example: 35% 3HX; 40% 3HX; 45% 3HX; 50% 3HX; 55% 3HX 60% 3HX; 65% 3HX; 70% 3HX; 75% 3HX; 80% 3HX; 85% 3HX; 90% 3HX by weight of the copolymer.

PHAs for use in the methods, compositions and pellets described in this invention are selected from: PHB or a Type 1 PHB copolymer; a PHA blend of PHB with a Type 1 PHB copolymer where the PHB content by weight of PHA in the PHA blend is in the range of 5% to 95% by weight of the PHA in the PHA blend; a PHA blend of PHB with a Type 2 PHB copolymer where the PHB content by weight of the PHA in the PHA blend is in the range of 5% to 95% by weight of the PHA in the PHA blend; a PHA blend of a Type 1 PHB copolymer with a different Type 1 PHB copolymer and where the content of the first Type 1 PHB copolymer is in the range of 5% to 95% by weight of the PHA in the PHA blend; a PHA blend of a Type 1 PHB copolymer with a Type 2 PHA copolymer where the content of the Type 1 PHB copolymer is in the range of 30% to 95% by weight of the PHA in the PHA blend; a PHA blend of PHB with a Type 1 PHB copolymer and a Type 2 PHB copolymer where the PHB content is in the range of 10% to 90% by weight of the PHA in the PHA blend, where the Type 1 PHB copolymer content is in the range of 5% to 90% by weight of the PHA in the PHA blend and where the Type 2 PHB copolymer content is in the range of 5% to 90% by weight of the PHA in the PHA blend.

The PHA blend of PHB with a Type 1 PHB copolymer is a blend of PHB with PHB3HP where the PHB content in the PHA blend is in the range of 5% to 90% by weight of the PHA in the PHA blend and the 3HP content in the PHB3HP is in the range of 7% to 15% by weight of the PHB3HP.

The PHA blend of PHB with a Type 1 PHB copolymer is a blend of PHB with PHB3HV where the PHB content of the PHA blend is in the range of 5% to 90% by weight of the PHA in the PHA blend and the 3HV content in the PHB3HV is in the range of 4% to 22% by weight of the PHB3HV.

The PHA blend of PHB with a Type 1 PHB copolymer is a blend of PHB with PHB4HB where the PHB content of the PHA blend is in the range of 5% to 90% by weight of the PHA in the PHA blend and the 4HB content in the PHB4HB is in the range of 4% to 15% by weight of the PHB4HB.

The PHA blend of PHB with a Type 1 PHB copolymer is a blend of PHB with PHB4HV where the PHB content of the PHA blend is in the range of 5% to 90% by weight of the PHA in the PHA blend and the 4HV content in the PHB4HV is in the range of 4% to 15% by weight of the PHB4HV.

The PHA blend of PHB with a Type 1 PHB copolymer is a blend of PHB with PHB5HV where the PHB content of the PHA blend is in the range of 5% to 90% by weight of the PHA in the PHA blend and the 5HV content in the PHB5HV is in the range of 4% to 15% by weight of the PHB5HV.

The PHA blend of PHB with a Type 1 PHB copolymer is a blend of PHB with PHB3HH where the PHB content of the PHA blend is in the range of 5% to 90% by weight of the PHA in the PHA blend and the 3HH content in the PHB3HH is in the range of 4% to 15% by weight of the PHB3HH.

The PHA blend of PHB with a Type 1 PHB copolymer is a blend of PHB with PHB3HX where the PHB content of the PHA blend is in the range of 5% to 90% by weight of the PHA in the PHA blend and the 3HX content in the PHB3HX is in the range of 4% to 15% by weight of the PHB3HX.

The PHA blend is a blend of a Type 1 PHB copolymer selected from the group PHB3HV, PHB3HP, PHB4HB, PHBV, PHV4HV, PHB5HV, PHB3HH and PHB3HX with a second Type 1 PHB copolymer which is different from the first Type 1 PHB copolymer and is selected from the group PHB3HV, PHB3HP, PHB4HB, PHBV, PHV4HV, PHB5HV, PHB3HH and PHB3HX where the content of the First Type 1 PHB copolymer in the PHA blend is in the range of 10% to 90% by weight of the total PHA in the blend.

The PHA blend of PHB with a Type 2 PHB copolymer is a blend of PHB with PHB4HB where the PHB content in the PHA blend is in the range of 30% to 95% by weight of the PHA in the PHA blend and the 4HB content in the PHB4HB is in the range of 20% to 60% by weight of the PHB4HB.

The PHA blend of PHB with a Type 2 PHB copolymer is a blend of PHB with PHB5HV where the PHB content in the PHA blend is in the range of 30% to 95% by weight of the PHA in the PHA blend and the HIV content in the PHB5HV is in the range of 20% to 60% by weight of the PHB5HV.

The PHA blend of PHB with a Type 2 PHB copolymer is a blend of PHB with PHB3HH where the PHB content in the PHA blend is in the range of 35% to 95% by weight of the PHA in the PHA blend and the 3HH content in the PHB3HH is in the range of 35% to 90% by weight of the PHB3HX.

The PHA blend of PHB with a Type 2 PHB copolymer is a blend of PHB with PHB3HX where the PHB content in the PHA blend is in the range of 30% to 95% by weight of the PHA in the PHA blend and the 3HX content in the PHB3HX is in the range of 35% to 90% by weight of the PHB3HX.

The PHA blend is a blend of PHB with a Type 1 PHB copolymer and a Type 2 PHB copolymer where the PHB content in the PHA blend is in the range of 10% to 90% by weight of the PHA in the PHA blend, the Type 1 PHB copolymer content of the PHA blend is in the range of 5% to 90% by weight of the PHA in the PHA blend and the Type 2 PHB copolymer content in the PHA blend is in the range of 5% to 90% by weight of the PHA in the PHA blend.

For example, a PHA blend can have a PHB content in the PHA blend in the range of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HV content in the PHA blend in the range 5% to 90% by weight of the PHA in the PHA blend, where the 3HV content in the PHB3HV is in the range of 3% to 22% by weight of the PHB3HV, and a PHBHX content in the PHA blend in the range of 5% to 90% by weight of the PHA in the PHA blend where the 3HX content in the PHBHX is in the range of 35% to 90% by weight of the PHBHX.

For example, a PHA blend can have a PHB content in the PHA blend in the range of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HV content in the PHA blend in the range 5% to 90% by weight of the PHA in the PHA blend, where the 3HV content in the PHB3HV is in the range of 3% to 22% by weight of the PHB3HV, and a PHB4HB content in the PHA blend in the range of 5% to 90% by weight of the PHA in the PHA blend where the 4HB content in the PHB4HB is in the range of 20% to 60% by weight of the PHB4HB.

For example, a PHA blend can have a PHB content in the PHA blend in the range of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HV content in the PHA blend in the range 5% to 90% by weight of the PHA in the PHA blend, where the 3HV content in the PHB3HV is in the range of 3% to 22% by weight of the PHB3HV, and a PHB5HV content in the PHA blend in the range of 5% to 90% by weight of the PHA in the PHA blend where the 5HV content in the PHB5HV is in the range of 20% to 60% by weight of the PHB5HV.

For example, a PHA blend can have a PHB content in the PHA blend in the range of 10% to 90% by weight of the PHA in the PHA blend, a PHB4HB content in the PHA blend in the range 5% to 90% by weight of the PHA in the PHA blend, where the 4HB content in the PHB4HB is in the range of 4% to 15% by weight of the PHB4HB, and a PHB4HB content in the PHA blend in the range of 5% to 90% by weight of the PHA in the PHA blend where the 4HB content in the PHB4HB is in the range of 20% to 60% by weight of the PHB4HB.

For example, a PHA blend can have a PHB content in the PHA blend in the range of 10% to 90% by weight of the PHA in the PHA blend, a PHB4HB content in the PHA blend in the range 5% to 90% by weight of the PHA in the PHA blend, where the 4HB content in the PHB4HB is in the range of 4% to 15% by weight of the PHB4HB, and a PHB5HV content in the PHA blend in the range of 5% to 90% by weight of the PHA in the PHA blend and where the 5HV content in the PHB5HV is in the range of 30% to 90% by weight of the PHB5HV.

For example, a PHA blend can have a PHB content in the PHA blend in the range of 10% to 90% by weight of the PHA in the PHA blend, a PHB4HB content in the PHA blend in the range 5% to 90% by weight of the PHA in the PHA blend, where the 4HB content in the PHB4HB is in the range of 4% to 15% by weight of the PHB4HB, and a PHB3HX content in the PHA blend in the range of 5% to 90% by weight of the PHA in the PHA blend and where the 3HX content in the PHB3HX is in the range of 35% to 90% by weight of the PHB3HX.

For example, a PHA blend can have a PHB content in the PHA blend in the range of 10% to 90% by weight of the PHA in the PHA blend, a PHB4HV content in the PHA blend in the range 5% to 90% by weight of the PHA in the PHA blend, where the 4HV content in the PHB4HV is in the range of 3% to 15% by weight of the PHB4HV, and a PHB5HV content in the PHA blend in the range of 5% to 90% by weight of the PHA in the PHA blend where the 5HV content in the PHB5HV is in the range of 30% to 90% by weight of the PHB5HV.

For example, a PHA blend can have a PHB content in the PHA blend in the range of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HH content in the PHA blend in the range 5% to 90% by weight of the PHA in the PHA blend, where the 3HH content in the PHB3HH is in the range of 3% to 15% by weight of the PHB3HH, and a PHB4HB content in the PHA blend in the range of 5% to 90% by weight of the PHA in the PHA blend where the 4HB content in the PHB4HB is in the range of 20% to 60% by weight of the PHB4HB.

For example, a PHA blend can have a PHB content in the PHA blend in the range of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HH content in the PHA blend in the range 5% to 90% by weight of the PHA in the PHA blend, where the 3HH content in the PHB3HH is in the range of 3% to 15% by weight of the PHB3HH, and a PHB5HV content in the PHA blend in the range of 5% to 90% by weight of the PHA in the PHA blend where the 5HV content in the PHB5HV is in the range of 20% to 60% by weight of the PHB5HV.

For example, a PHA blend can have a PHB content in the PHA blend in the range of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HH content in the PHA blend in the range 5% to 90% by weight of the PHA in the PHA blend, where the 3HH content in the PHB3HH is in the range of 3% to 15% by weight of the PHB3HH, and a PHB3HX content in the PHA blend in the range of 5% to 90% by weight of the PHA in the PHA blend where the 3HX content in the PHB3HX is in the range of 35% to 90% by weight of the PHB3HX.

For example, a PHA blend can have a PHB content in the PHA blend in the range of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HX content in the PHA blend in the range 5% to 90% by weight of the PHA in the PHA blend, where the 3HX content in the PHB3HX is in the range of 3% to 12% by weight of the PHB3HX, and a PHB3HX content in the PHA blend in the range of 5% to 90% by weight of the PHA in the PHA blend where the 3HX content in the PHB3HX is in the range of 35% to 90% by weight of the PHB3HX.

For example, a PHA blend can have a PHB content in the PHA blend in the range of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HX content in the PHA blend in the range 5% to 90% by weight of the PHA in the PHA blend, where the 3HX content in the PHB3HX is in the range of 3% to 12% by weight of the PHB3HX, and a PHB4HB content in the PHA blend in the range of 5% to 90% by weight of the PHA in the PHA blend where the 4HB content in the PHB4HB is in the range of 20% to 60% by weight of the PHB4HB.

For example, a PHA blend can have a PHB content in the PHA blend in the range of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HX content in the PHA blend in the range 5% to 90% by weight of the PHA in the PHA blend, where the 3HX content in the PHB3HX is in the range of 3% to 12% by weight of the PHB3HX, and a PHB5HV content in the PHA blend in the range of 5% to 90% by weight of the PHA in the PHA blend where the 5HV content in the PHB5HV is in the range of 20% to 60% by weight of the PHB5HV.

The PHA blend is a blend as disclosed in U.S. Published Application No. US 2004/0220355, by Whitehouse, published Nov. 4, 2004, which is incorporated herein by reference in its entirety.

Microbial systems for producing the PHB copolymer PHBV are disclosed in, e.g., U.S. Pat. No. 4,477,654 to Holmes, which is incorporated herein by reference in its entirety. U.S. Published Application No. US 2002/0164729 (also incorporated herein by reference in its entirety) by Skraly and Sholl describes useful systems for producing the PHB copolymer PHB4HB. Useful processes for producing the PHB copolymer PHB3HH have been described (Lee et al., 2000, Biotechnology and Bioengineering 67:240-244; Park et al., 2001, Biomacromolecules 2:248-254). Processes for producing the PHB copolymers PHB3HX have been described by Matsusaki et al. (Biomacromolecules 2000, 1:17-22).

In determining the molecular weight techniques such as gel permeation chromatography (GPC) can be used. In the methodology, a polystyrene standard is utilized. The PHA can have a polystyrene equivalent weight average molecular weight (in daltons) of at least 500, at least 10,000, or at least 50,000 and/or less than 2,000,000, less than 1,000,000, less than 1,500,000, and less than 800,000. In certain embodiments, preferably, the PHAs generally have a weight-average molecular weight in the range of 100,000 to 700,000. For example, the molecular weight range for PHB and Type 1 PHB copolymers for use in this application are in the range of 400,000 daltons to 1.5 million daltons as determined by GPC method and the molecular weight range for Type 2 PHB copolymers for use in the application 100,000 to 1.5 million daltons.

In certain embodiments, the PHA can have a linear equivalent weight average molecular weight of from about 150,000 Daltons to about 500,000 Daltons and a polydispersity index of from about 2.5 to about 8.0. As used herein, weight average molecular weight and linear equivalent weight average molecular weight are determined by gel permeation chromatography, using, e.g., chloroform as both the eluent and diluent for the PHA samples. Calibration curves for determining molecular weights are generated using linear polystyrenes as molecular weight standards and a ‘log MW vs elution volume’ calibration method.

Blends of PHA with Aromatic/Aliphatic Polyester

In certain embodiments, the polymers for use in the methods and compositions are blended in the presence of additives, branching agents and cross-linking agents to form compositions with improved properties. The percentages of PHA to aromatic/aliphatic polyesters are 5% to 95% by weight. In certain compositions of the invention, the percentage of PHA to aromatic/aliphatic polyester of the total polymer compositions ranges from about 95% PHA to about 5% aromatic/aliphatic polyester or about 50% aromatic/aliphatic polyester to about 50% PHA. For example the PHA/aromatic/aliphatic polyester ratio can be 95/5, 90/10, 85/15, 80/20, 75/25, 70/30, 65/35, 60/40, 55/45 or 50/50.

PHAs and biodegradable aromatic/aliphatic polyesters can be combined to make blends of the polymers, In one embodiment, the blend is homogeneous.

The amount of PHA in the overall blend is 5 to 95% by weight of the total polymer blend The selection and amount of each polymer will effect the softness, stiffness, texture, toughness, and other properties of the final product as will be understood by those of ordinary skill in the art. Typically, the PHA component is present in the blend in an amount of from 5% to 95%, preferably from about 10% to about 50%, by total weight of the total polymer components of the composition.

In certain embodiments, the amount of PHA in the overall blend can be about 1% by weight, about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90%, about 95%, or about 99% by weight. The selection and amount of each polymer will effect the softness, stiffness, texture, toughness, and other properties of the final product as will be understood by those of ordinary skill in the art. Typically, the PHA component is present in the blend in an amount of from about 10% to 95%, preferably from about 15% to about 85%, more preferably from about 20% to about 80%, by total weight of the total polymer components.

Each polymer component can contain a single polymer species or a blend of two or more species. For instance, and PHA component can in turn be a blend of PHA species as described above. Likewise, the biodegradable aromatic/aliphatic polyester component can be a mixture or blend of more than one biodegradable aromatic/aliphatic polyester.

In any of the compositions, pellets or methods disclosed herein, the biodegradable aromatic/aliphatic polyester can include aluminum hydroxy diphosphate and a carboxylate salt.

It has been found that PHA polyesters with higher levels of crystallinity are particularly useful in this invention, for example, the homopolymer PHB, the copolymer PHBV with 3HV levels of from 3% to 25%, copolymers PHB3HP with 3HP levels of 3 to 10%, PHBH with 3HH levels from 3 to 20%. The PHB homopolymer or copolymers of 3HB with low levels of copolymers such as 3HP, 3HH, 4HB, 4HV of between 3 and 10% are particularly useful. Where the PHA copolymer is isodimorphic, as is the case with the 3HV comonomer then a 3HV content of between 3 and 25% is preferred.

Methods for making and using thermoplastic compositions are well known to those of skill in the art, and skilled practitioners will appreciate that the biodegradable blends of the present invention can be used in a wide range of applications and further, as is known to skilled practitioners, can contain one or more additive, e.g., a plasticizer, nucleating agent, filler, antioxidant, ultraviolet stabilizer, lubricant, slip/antiblock, pigment, flame retardant, reinforcing, mold release, and/or antistatic agent.

Branched Polyhydroxyalkanoates and Branched Aromatic/Aliphatic Polyesters

The term “branched polymer” refers to a PHA, or aromatic/aliphatic polyester with branching of the chain and/or cross-linking of two or more chains. Branching on side chains is also contemplated. Branching can be accomplished by various methods. Polyhydroxyalkanoate polymer described above can be branched by branching agents by free-radical-induced cross-linking of the polymer. In certain embodiment, the PHA is branched prior to combination in the method. In other embodiments, the PHA reacted with peroxide in the methods of the invention. The branching increases the melt strength of the polymer. Polyhydroxyalkanoate polymers can be branched in any of the ways described in U.S. Pat. Nos. 6,620,869, 7,208,535, 6,201,083, 6,156,852, 6,248,862, 6,201,083 and 6,096,810 all of which are incorporated herein by reference in their entirety.

The polymers of the invention can be branched according to any of the methods disclosed in PCT/US09/003687 titled “Methods For Branching PHA Using Thermolysis” or PCT/US09/003675 titled “Branched PHA Compositions, Methods For Their Production, And Use In Applications”, both of which were filed in English on Jun. 19, 2009, and designated the United States. These applications are incorporated by reference herein in their entirety.

The invention provides branched PHA copolymer blend compositions with aromatic/aliphatic polymers (e.g., PBAT) that do not require the use of a compatibilizer for mixing and blending that other thermoplastic polymer blend compositions require. In these other compositions the compatibilizer is necessary to improve the properties of the blends and increase the compatibility of the polymer composition, especially immiscible polymers.

Branching Agents

The branching agents, also referred to a free radical initiator, for use in the compositions and method described herein include organic peroxides. Peroxides are reactive molecules, and can react with polymer molecules or previously branched polymers by removing a hydrogen atom from the polymer backbone, leaving behind a radical. Polymer molecules having such radicals on their backbone are free to combine with each other, creating branched polymer molecules. Branching agents are selected from any suitable initiator known in the art, such as peroxides, azo-dervatives (e.g., azo-nitriles), peresters, and peroxycarbonates. Suitable peroxides for use in the present invention include, but are not limited to, organic peroxides, for example dialkyl organic peroxides such as 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-bis(t-butylperoxy)-2,5-dimethylhexane (available from Akzo Nobel as TRIGANOX 101), 2,5-dimethyl-di(t-butylperoxy)hexyne-3, di-t-butyl peroxide, dicumyl peroxide, benzoyl peroxide, di-t-amyl peroxide, t-amylperoxy-2-ethylhexylcarbonate (TAEC), t-butyl cumyl peroxide, n-butyl-4,4-bis(t-butylperoxy)valerate, 1,1-di(t-butylperoxy)-3,3,5-trimethyl-cyclohexane, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane (CPK), 1,1-di(t-butylperoxy)cyclohexane, 1,1-di(t-amylperoxy)-cyclohexane, 2,2-di(t-butylperoxy)butane, ethyl-3,3-di(t-butylperoxy)butyrate, 2,2-di(t-amylperoxy)propane, ethyl-3,3-di(t-amylperoxy)butyrate, t-butylperoxy-acetate, t-amylperoxyacetate, t-butylperoxybenzoate, t-amylperoxybenzoate, di-t-butyldiperoxyphthalate, and the like. Combinations and mixtures of peroxides can also be used. Examples of free radical initiators include those mentioned herein, as well as those described in, e.g., Polymer Handbook, 3^(rd) Ed., J. Brandrup & E. H. Immergut, John Wiley and Sons, 1989, Ch. 2. Irradiation (e.g., e-beam or gamma irradiation) can also be used to generate PHA branching.

The efficiency of branching and crosslinking of the polymer(s) can also be significantly enhanced by the dispersion of organic peroxides in a cross-linking agent, such as a polymerizable (i.e., reactive) plasticizers. The polymerizable plasticizer should contain a reactive functionality, such as a reactive unsaturated double bond, which increases the overall branching and crosslinking efficiency.

As discussed above, when peroxides decompose, they form very high energy radicals that can extract a hydrogen atom from the polymer backbone. These radicals have short half-lives, thereby limiting the population of branched molecules that is produced during the active time period.

Additives

In certain embodiments, various additives are added to the compositions. Examples of these additives include antioxidants, pigments, thermal and UV absorbers or stabilizers (such as TINUVIN® 234 and 326), inorganic and organic fillers, plasticizers, nucleating agents, and radical scavengers, anti-slip agents, anti- blocking agents, waxes, and radical scavengers. Additionally, polyfunctional branching agents such as divinyl benzene, trially cyanurate and the like may be added. The branching agent and/or cross-linking agent is added to one or more of these for easier incorporation into the polymer. For instance, the branching agent and/or cross-linking agent is mixed with a plasticizer, e.g., a non-reactive plasticizer, e.g., a citric acid ester, and then compounded with the polymer under conditions to induce branching.

The additives are included in the thermoplastic compositions at a concentration of about 0.05 to about 20% by weight of the total composition. For example, the range is certain embodiments is about 0.05 to about 5% of the total composition.

The additive(s) can also be prepared as a masterbatch for example, by incorporating the additive(s) in a PHA blend and producing pellets of the resultant composition for addition to subsequent processing. In a masterbatch the concentration of the additive(s) is (are) higher than the final amount for the product to allow for proportionate mixing of the additive in the final composition.

The additive is any compound known to those of skill in the art to be useful in the production of thermoplastics. Exemplary additives include, e.g., plasticizers (e.g., to increase flexibility of a thermoplastic composition), antioxidants (e.g., to protect the thermoplastic composition from degradation by ozone or oxygen), ultraviolet stabilizers (e.g, to protect against weathering), lubricants (e.g., to reduce friction), pigments (e.g., to add color to the thermoplastic composition), flame retardants, fillers, reinforcing, mold release, and antistatic agents. It is well within the skilled practitioner's abilities to determine whether an additive should be included in a thermoplastic composition and, if so, what additive and the amount that should be added to the composition.

In poly-3-hydroxybutyrate compositions, for example, plasticizers are often used to change the glass transition temperature and modulus of the composition, but surfactants may also be used. Lubricants may also be used, e.g., in injection molding applications. Plasticizers, surfactants and lubricants may all therefore be included in the overall composition.

In other embodiments, the blend includes one or more plasticizers. Examples of plasticizers include phthalic compounds (including, but not limited to, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, di-n-octyl phthalate, di-2-ethylhexyl phthalate, diisooctyl phthalate, dicapryl phthalate, dinonyl phthalate, diisononyl phthalate, didecyl phthalate, diundecyl phthalate, dilauryl phthalate, ditridecyl phthalate, dibenzyl phthalate, dicyclohexyl phthalate, butyl benzyl phthalate, octyl decyl phthalate, butyl octyl phthalate, octyl benzyl phthalate, n-hexyl n-decyl phthalate, n-octyl phthalate, and n-decyl phthalate), phosphoric compounds (including, but not limited to, tricresyl phosphate, trioctyl phosphate, triphenyl phosphate, octyl diphenyl phosphate, cresyl diphenyl phosphate, and trichloroethyl phosphate), adipic compounds (including, but not limited to, dibutoxyethoxyethyl adipate (DBEEA), dioctyl adipate, diisooctyl adipate, di-n-octyl adipate, didecyl adipate, diisodecyl adipate, n-octyl n-decyl adipate, n-heptyl adipate, and n-nonyl adipate), sebacic compounds (including, but not limited to, dibutyl sebacate, dioctyl sebacate, diisooctyl sebacate, and butyl benzyl sebacate), azelaic compounds, citric compounds (including, but not limited to, triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl tributyl citrate, and acetyl trioctyl citrate), glycolic compounds (including, but not limited to, methyl phthalyl ethyl glycolate, ethyl phthalyl ethyl glycolate, and butyl phthalyl ethyl glycolate), trimellitic compounds (including, but not limited to, trioctyl trimellitate and tri-n-octyl n-decyl trimellitate), phthalic isomer compounds (including, but not limited to, dioctyl isophthalate and dioctyl terephthalate), ricinoleic compounds (including, but not limited to, methyl acetyl, recinoleate and butyl acetyl recinoleate), polyester compounds (including, but not limited to reaction products of diols selected from butane diol, ethylene glycol, propane 1,2 diol, propane 1,3 diol, polyethylene glycol, glycerol, diacids selected from adipic acid, succinic acid, succinic anhydride and hydroxyacids such as hydroxystearic acid, epoxidized soy bean oil, chlorinated paraffins, chlorinated fatty acid esters, fatty acid compounds, plant oils, pigments, and acrylic compounds. The plasticizers may be used either alone respectively or in combinations with each other.

In certain embodiments, the compositions and methods of the invention include one or more surfactants. Surfactants are generally used to de-dust, lubricate, reduce surface tension, and/or densify. Examples of surfactants include, but are not limited to mineral oil, castor oil, and soybean oil. One mineral oil surfactant is Drakeol 34, available from Penreco (Dickinson, Tex., USA). Maxsperse W-6000 and W-3000 solid surfactants are available from Chemax Polymer Additives (Piedmont, S.C., USA). Non-ionic surfactants with HLB values ranging from about 2 to about 16 can be used, examples being TWEEN-20, TWEEN-65, Span-40 and Span 85.

Anionic surfactants include: aliphatic carboxylic acids such as lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid; fatty acid soaps such as sodium salts or potassium salts of the above aliphatic carboxylic acids; N-acyl-N-methylglycine salts, N-acyl-N-methyl-beta-alanine salts, N-acylglutamic acid salts, polyoxyethylene alkyl ether carboxylic acid salts, acylated peptides, alkylbenzenesulfonic acid salts, alkylnaphthalenesulfonic acid salts, naphthalenesulfonic acid salt-formalin polycondensation products, melaminesulfonic acid salt-formalin polycondensation products, dialkylsulfosuccinic acid ester salts, alkyl sulfosuccinate disalts, polyoxyethylene alkylsulfosuccinic acid disalts, alkylsulfoacetic acid salts, (alpha-olefinsulfonic acid salts, N-acylmethyltaurine salts, sodium dimethyl 5-sulfoisophthalate, sulfated oil, higher alcohol sulfuric acid ester salts, polyoxyethylene alkyl ether sulfuric acid salts, secondary higher alcohol ethoxysulfates, polyoxyethylene alkyl phenyl ether sulfuric acid salts, monoglysulfate, sulfuric acid ester salts of fatty acid alkylolamides, polyoxyethylene alkyl ether phosphoric acid salts, polyoxyethylene alkyl phenyl ether phosphoric acid salts, alkyl phosphoric acid salts, sodium alkylamine oxide bistridecylsulfosuccinates, sodium dioctylsulfosuccinate, sodium dihexylsulfosuccinate, sodium dicyclohexylsulfosuccinate, sodium diamylsulfosuccinate, sodium diisobutylsulfosuccinate, alkylamine guanidine polyoxyethanol, disodium sulfosuccinate ethoxylated alcohol half esters, disodium sulfosuccinate ethoxylated nonylphenol half esters, disodium isodecylsulfosuccinate, disodium N-octadecylsulfosuccinamide, tetrasodium N-(1,2-dicarboxyethyl)-N-octadecylsulfosuccinamide, disodium mono- or didodecyldiphenyl oxide disulfonates, sodium diisopropylnaphthalenesulfonate, and neutralized condensed products from sodium naphthalenesulfonate.

One or more lubricants can also be added to the compositions and methods of the invention. Lubricants are normally used to reduce sticking to hot metal surfaces during processing and can include polyethylene, paraffin oils, and paraffin waxes in combination with metal stearates. Other lubricants include stearic acid, amide waxes, ester waxes, metal carboxylates, and carboxylic acids. Lubricants are normally added to polymers in the range of about 0.1 percent to about 1 percent by weight, generally from about 0.7 percent to about 0.8 percent by weight of the compound. Solid lubricants is warmed and melted before or during processing of the blend.

One or more anti-microbial agents can also be added to the compositions and methods of the invention. An anti-microbial is a substance that kills or inhibits the growth of microorganisms such as bacteria, fungi, or protozoans, as well as destroying viruses. Antimicrobial drugs either kill microbes (microbicidal) or prevent the growth of microbes (microbistatic). A wide range of chemical and natural compounds are used as antimicrobials, including but not limited to: organic acids, essential oils, cations and elements (e.g., colloidal silver). Commercial examples include but are not limited to PolySept® Z, UDA and AGION.®

PolySept Z (available from PolyChem Alloy) is a organic salt based, non-migratory antimicrobial. “UDA” is Urtica dioica agglutinin. AgION is a silver compound. Amical 48 is diiodomethyl p-tolyl sulfone. In certain aspects the antimicrobial agent slows down degradation of the composition.

In film applications of the compositions and methods described herein, anti-lock masterbatch is also added. A suitable example is a slip anti-block masterbatch mixture of erucamide (20% by weight) diatomaceous earth (15% by weight) nucleant masterbatch (3% by weight), pelleted into PHA (62% by weight).

Cross-Linking Agents

Cross-linking agent, also referred to as co-agents, used in the methods and compositions of the invention are cross-linking agents comprising two or more reactive functional groups such as epoxides or double bonds. These cross-linking agents modify the properties of the polymer. These properties include, but are not limited to, melt strength or toughness. One type of cross-linking agent is an “epoxy functional compound.” As used herein, “epoxy functional compound” is meant to include compounds with two or more epoxide groups capable of increasing the melt strength of polyhydroxyalkanoate polymers by branching, e.g., end branching as described above.

When an epoxy functional compound is used as the cross-linking agent in the disclosed methods, a branching agent is optional. As such one embodiment of the invention is a method of branching a starting polyhydroxyalkanoate polymer (PHA), comprising reacting a starting PHA with an epoxy functional compound. Alternatively, the invention is a method of branching a starting polyhydroxyalkanoate polymer, comprising reacting a starting PHA, a branching agent and an epoxy functional compound. Alternatively, the invention is a method of branching a starting polyhydroxyalkanoate polymer, comprising reacting a starting PHA, and an epoxy functional compound in the absence of a branching agent. Such epoxy functional compounds can include epoxy-functional, styrene-acrylic polymers (such as, but not limited to, e.g., Joncryl ADR-4368 (BASF), or MP-40 (Kaneka)), acrylic and/or polyolefin copolymers and oligomers containing glycidyl groups incorporated as side chains (such as, but not limited to, e.g., LOTADER® (Arkema), poly(ethylene-glycidyl methacrylate-co-methacrylate)), and epoxidized oils (such as, but not limited to, e.g., epoxidized soybean, olive, linseed, palm, peanut, coconut, seaweed, cod liver oils, or mixtures thereof, e.g., Merginat® ESBO (Hobum, Hamburg, Germany)and Edenol® B 316 (Cognis, Dusseldorf, Germany)).

For example, reactive acrylics or functional acrylics cross-linking agents are used to increase the molecular weight of the polymer in the branched polymer compositions described herein. Such cross-linking agents are sold commercially. BASF, for instance, sells multiple compounds under the trade name “Joncryl”, which are described in U.S. Pat. No. 6,984,694 to Blasius et al., “Oligomeric chain extenders for processing, post-processing and recycling of condensation polymers, synthesis, compositions and applications”, incorporated herein by reference in its entirety. One such compound is Joncryl ADR-4368CS, which is styrene glycidyl methacrylate and is discussed below. Another is MP-40 (Kaneka). And still another is Petra line from Honeywell, see for example, U.S. Pat. No. 5,723,730. Such polymers are often used in plastic recycling (e.g., in recycling of polyethylene terephthalate) to increase the molecular weight (or to mimic the increase of molecular weight) of the polymer being recycled. Such polymers often have the general structure:

-   -   R₁ and R₂ are H or alkyl     -   R₃ is alkyl     -   x and y are 1-20     -   z is 2-20

E.I. du Pont de Nemours & Company sells multiple reactive compounds under the trade name Elvaloy®, which are ethylene copolymers, such as acrylate copolymers, elastomeric terpolymers, and other copolymers. One such compound is Elvaloy PTW, which is a copolymer of ethylene-n-butyl acrylate and glycidyl methacrylate. Omnova sells similar compounds under the trade names “SX64053,” “SX64055,” and “SX64056.” Other entities also supply such compounds commercially.

Specific polyfunctional polymeric compounds with reactive epoxy functional groups are the styrene-acrylic copolymers. These materials are based on oligomers with styrene and acrylate building blocks that have glycidyl groups incorporated as side chains. A high number of epoxy groups per oligomer chain are used, for example 5, greater than 10, or greater than 20. These polymeric materials generally have a molecular weight greater than 3000, specifically greater than 4000, and more specifically greater than 6000. These are commercially available from S. C. Johnson Polymer, LLC (now owned by BASF) under the trade name JONCRYL, ADR 4368 material. Other types of polyfunctional polymer materials with multiple epoxy groups are acrylic and/or polyolefin copolymers and oligomers containing glycidyl groups incorporated as side chains. A further example of such a polyfunctional carboxy-reactive material is a co- or ter-polymer including units of ethylene and glycidyl methacrylate (GMA), available under the trade name LOTADER® resin, sold by Arkema. These materials can further comprise methacrylate units that are not glycidyl. An example of this type is poly(ethylene-glycidyl methacrylate-co-methacrylate).

Fatty acid esters or naturally occurring oils containing epoxy groups (epoxidized) can also be used. Examples of naturally occurring oils are olive oil, linseed oil, soybean oil, palm oil, peanut oil, coconut oil, seaweed oil, cod liver oil, or a mixture of these compounds. Particular preference is given to epoxidized soybean oil (e.g., Merginat® ESBO from Hobum, Hamburg, or Edenol® B 316 from Cognis, Dusseldorf), but others may also be used.

Another type of cross-linking agent are agents with two or moredouble bonds. Cross-linking agents with two or more double bond cross-link PHAs by after reacting at the double bonds. Examples of these include: diallyl phthalate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, diethylene glycol dimethacrylate, bis(2-methacryloxyethyl)phosphate.

In general, it appears that compounds with terminal epoxides may perform better than those with epoxide groups located elsewhere on the molecule.

Compounds having a relatively high number of end groups are the most desirable. Molecular weight may also play a role in this regard, and compounds with higher numbers of end groups relative to their molecular weight (e.g., the Joncryls are in the 3000-4000 g/mol range) are likely to perform better than compounds with fewer end groups relative to their molecular weight (e.g., the Omnova products have molecular weights in the 100,000-800,000 g/mol range).

Nucleating Agents

For instance, an optional nucleating agent is added to the composition to aid in its crystallization. Nucleating agents for various polymers are simple substances, metal compounds including composite oxides, for example, carbon black, calcium carbonate, synthesized silicic acid and salts, silica, zinc white, clay, kaolin, basic magnesium carbonate, mica, talc, quartz powder, diatomite, dolomite powder, titanium oxide, zinc oxide, antimony oxide, barium sulfate, calcium sulfate, alumina, calcium silicate, metal salts of organophosphates, and boron nitride; low-molecular organic compounds having a metal carboxylate group, for example, metal salts of such as octylic acid, toluic acid, heptanoic acid, pelargonic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, cerotic acid, montanic acid, melissic acid, benzoic acid, p-tert-butylbenzoic acid, terephthalic acid, terephthalic acid monomethyl ester, isophthalic acid, and isophthalic acid monomethyl ester; high-molecular organic compounds having a metal carboxylate group, for example, metal salts of such as: carboxyl-group-containing polyethylene obtained by oxidation of polyethylene; carboxyl-group-containing polypropylene obtained by oxidation of polypropylene; copolymers of olefins, such as ethylene, propylene and butene-1, with acrylic or methacrylic acid; copolymers of styrene with acrylic or methacrylic acid; copolymers of olefins with maleic anhydride; and copolymers of styrene with maleic anhydride; high-molecular organic compounds, for example: alpha-olefins branched at their 3-position carbon atom and having no fewer than 5 carbon atoms, such as 3,3 dimethylbutene-1,3-methylbutene-1,3-methylpentene-1,3-methylhexene-1, and 3,5,5-trimethylhexene-1; polymers of vinylcycloalkanes such as vinylcyclopentane, vinylcyclohexane, and vinylnorbornane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; poly(glycolic acid); cellulose; cellulose esters; and cellulose ethers; phosphoric or phosphorous acid and its metal salts, such as diphenyl phosphate, diphenyl phosphite, metal salts of bis(4-tert-butylphenyl)phosphate, and methylene bis-(2,4-tert-butylphenyl)phosphate; sorbitol derivatives such as bis(p-methylbenzylidene)sorbitol and bis(p-ethylbenzylidene)sorbitol; and thioglycolic anhydride, p-toluenesulfonic acid and its metal salts. The above nucleating agents may be used either alone or in combinations with each other. In particular embodiments, the nucleating agent is cyanuric acid. In certain embodiments, the nucleating agent can also be another polymer (e.g., polymeric nucleating agents such as NIB).

In certain embodiments, the nucleating agent is selected from: cyanuric acid, carbon black, mica talc, silica, boron nitride, clay, calcium carbonate, synthesized silicic acid and salts, metal salts of organophosphates, and kaolin. In particular embodiments, the nucleating agent is cyanuric acid.

In various embodiments, where the nucleating agent is dispersed in a liquid carrier, the liquid carrier is a plasticizer, e.g., a citric compound or an adipic compound, e.g., acetylcitrate tributyrate (Citroflex A4, Vertellus, Inc., High Point, N.C.), or DBEEA (dibutoxyethoxyethyl adipate), a surfactant, e.g., Triton X-100, TWEEN-20, TWEEN-65, Span-40 or Span 85, a lubricant, a volatile liquid, e.g., chloroform, heptane, or pentane, a organic liquid or water.

In other embodiments, the nucleating agent is aluminum hydroxy diphosphate or a compound comprising a nitrogen-containing heteroaromatic core. The nitrogen-containing heteroaromatic core is pyridine, pyrimidine, pyrazine, pyridazine, triazine, or imidazole.

In particular embodiments, the nucleating agent can include aluminum hydroxy diphosphate or a compound comprising a nitrogen-containing heteroaromatic core. The nitrogen-containing heteroaromatic core is pyridine, pyrimidine, pyrazine, pyridazine, triazine, or imidazole. The nucleant can have a chemical formula selected from the group consisting of

and combinations thereof, wherein each R1 is independently H, NR²R², OR², SR², SOR², SO₂R², CN, COR², CO₂R², CONR²R², NO₂, F, Cl, Br, or I; and each R² is independently H or C₁-C₆ alkyl.

The nucleating agent can be a nucleating agent as described in U.S. Pat. App. Pub. 2005/0209377, by Allen Padwa, which is herein incorporated by reference in its entirety.

Another nucleating agent for use in the compositions and methods described herein are milled as described in WO 2009/129499 titled “Nucleating Agents for Polyhydroxyalkanoates,” which was published in English and designated the United States, and which is herein incorporated by reference in its entirety. Briefly, the nucleating agent is milled in a liquid carrier until at least 5% of the cumulative solid volume of the nucleating agent exists as particles with a particle size of 5 microns or less. The liquid carrier allows the nucleating agent to be wet milled. In other embodiments, the nucleating agent is milled in liquid carrier until at least 10% of the cumulative solid volume, at least 20% of the cumulative solid volume, at least 30% or at least 40%-50% of the nucleating agent can exist as particles with a particle size of 5 microns or less, 2 microns or less or 1 micron or less. In alternative embodiments, the nucleating agents is milled by other methods, such as jet milling and the like. Additionally, other methods is utilized that reduce the particle size.

The cumulative solid volume of particles is the combined volume of the particles in dry form in the absence of any other substance. The cumulative solid volume of the particles is determined by determining the volume of the particles before dispersing them in a polymer or liquid carrier by, for example, pouring them dry into a graduated cylinder or other suitable device for measuring volume. Alternatively, cumulative solid volume is determined by light scattering.

Application of the Compositions

For the fabrication of useful articles, the compositions described herein are processed preferably at a temperature above the crystalline melting point of the polymers but below the decomposition point of any of the ingredients (e.g., the additives described above, with the exception of some branching agents) of the polymeric composition. While in heat plasticized condition, the polymeric composition is processed into a desired shape, and subsequently cooled to set the shape and induce crystallization. Such shapes can include, but are not limited to, a fiber, filament, film, sheet, rod, tube, bottle, or other shape. Such processing is performed using any art-known technique, such as, but not limited to, extrusion, injection molding, compression molding, blowing or blow molding (e.g., blown film, blowing of foam), calendaring, rotational molding, casting (e.g., cast sheet, cast film), or thermoforming.

The compositions are used to create, without limitation, a wide variety of useful products, e.g., automotive, consumer durable, construction, electrical, medical, and packaging products. For instance, the polymeric compositions is used to make, without limitation, films (e.g., packaging films, agricultural film, mulch film, erosion control, hay bale wrap, slit film, food wrap, pallet wrap, protective automobile and appliance wrap, etc.), golf tees, caps and closures, agricultural supports and stakes, paper and board coatings (e.g., for cups, plates, boxes, etc.), thermoformed products (e.g., trays, containers, lids, yoghurt pots, cup lids, plant pots, noodle bowls, moldings, etc.), housings (e.g., for electronics items, e.g., cell phones, PDA cases, music player cases, computer cases and the like), bags (e.g., trash bags, grocery bags, food bags, compost bags, etc.), hygiene articles (e.g., diapers, feminine hygiene products, incontinence products, disposable wipes, etc.), coatings for pelleted products (e.g., pelleted fertilizer, herbicides, pesticides, seeds, etc.), injection molded articles (writing instruments, utensils, disk cases, etc.), solution and spun fibers and melt blown fabrics and non-wovens (threads, yarns, wipes, wadding, disposable absorbent articles), blow moldings (deep containers, bottles, etc.) and foamed articles (cups, bowls, plates, packaging, etc.).

Thermoforming is a process that uses films or sheets of thermoplastic. The polymeric composition is processed into a film or sheet. The sheet of polymer is then placed in an oven and heated. When soft enough to be formed it is transferred to a mold and formed into a shape.

During thermoforming, when the softening point of a semi-crystalline polymer is reached, the polymer sheet begins to sag. The window between softening and droop is usually narrow. It can therefore be difficult to move the softened polymer sheet to the mold quickly enough. Branching the polymer can be used to increase the melt strength of the polymer so that the sheet maintains is more readily processed and maintains its structural integrity. Measuring the sag of a sample piece of polymer when it is heated is therefore a way to measure the relative size of this processing window for thermoforming.

Because the composition described herein have increased melt strength and increased processability, they are easier to convert to film or sheet form. They are therefore excellent candidates for thermoforming. Molded products include a number of different product types and, for example, including products such as disposable spoons, forks and knives, tubs, bowls, lids, cup lids, yogurt cups, and other containers, bottles and bottle-like containers, etc.

The compositions described herein can be processed into films of varying thickness, for example, films of uniform thickness ranging from 10-200 microns, for example, 20-75 microns, 75 to 150 microns, or from 50-100 microns. Film layers can additionally be stacked to form multilayer films of the same or varying thicknesses or compositions. For example, a film can comprise two, three, four or more layers, where the layers can include one or more layers of a composition or compositions of the invention combined with other polymer layers, such as PHA layers, or PLA layers and the like.

Blow molding, which is similar to thermoforming and is used to produce deep draw products such as bottles and similar products with deep interiors, also benefits from the increased elasticity and melt strength and reduced sag of the polymer compositions described herein.

Articles made from the compositions can be annealed according to any of the methods disclosed in WO 2010/008445, filed Jun. 19, 2009 and titled “Branched PHA Compositions, Methods For Their Production, And Use In Applications”, which was filed in English and designated the United States. This application is incorporated by reference herein in its entirety.

The compositions described herein are provided in any suitable form convenient for an intended application. For example, the composition is provided in pellet for subsequent production of films, coatings, moldings or other articles, or the films, coatings, moldings and other articles.

The specific examples below are to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever. Without further elaboration, it is believed that one skilled in the art can, based on the description herein, utilize the present invention to its fullest extent. All publications cited herein are hereby incorporated by reference in their entirety.

EXAMPLES Examples for PBAT-PHA Reactive Melt Blends Experimental Methods

Measurement of Melt Strength and Viscosity 101391 All oscillatory rheology measurements were performed using a TA Instruments AR2000 rheometer employing a strain amplitude of 1%. First, pellets (or powder) were molded into 25 mm diameter discs that were about 1200 microns in thickness. The disc specimens were molded in a compression molder set at about 165° C., with the molding time of about 30 seconds. These molded discs were then placed in between the 25 mm parallel plates of the AR2000 rheometer, equilibrated at 180° C., and subsequently cooled to 160° C. for the frequency sweep test. A gap of 800-900 microns was used, depending on the normal forces exerted by the polymer. The melt density of PHB was determined to be about 1.10 g/cm³ at 160° C.; this value was used in all the calculations.

Specifically, the specimen disc is placed between the platens of the parallel plate rheometer set at 180° C. After the final gap is attained, excess material from the sides of the platens is scraped. The specimen is then cooled to 160° C. where the frequency scan (from 625 rad/s to 0.10 rad/s) is then performed; frequencies lower than 0.1 rad/s are avoided because of considerable degradation over the long time it takes for these lower frequency measurements. The specimen loading, gap adjustment and excess trimming, all carried out with the platens set at 180° C., takes about 2½ minutes. This is controlled to within ±10 seconds to minimize variability and sample degradation. Cooling from 180° C. to 160° C. (test temperature) is accomplished in about four minutes. Exposure to 180° C. ensures a completely molten polymer, while testing at 160° C. ensures minimal degradation during measurement.

During the frequency sweep performed at 160° C., the following data are collected as a function of measurement frequency: η* or complex viscosity, G′ or elastic modulus (elastic or solid-like contribution to the viscosity) and G″ or loss modulus (viscous or liquid-like contribution to the viscosity). For purposes of simplicity, we will use G′ and η* measured at an imposed frequency of 0.25 rad/s as a measure of “melt strength” and viscosity.

Measurement of Melt Crystallization

A Perkin Elmer DSC is used to characterize the non-isothermal melt-crystallization kinetics of the subject PHB copolymers. In this test, the specimen (cut from a disc compression molded at 165° C. for one minute) is placed and crimped in the DSC sample pan. This test specimen is then exposed to 200° C. for one minute to melt all of the crystals; it is then cooled to 160° C. at 40° C./min and maintained at 160° C. for about 1 minute. The specimen is then cooled to −50° C. at a rate of about 10° C/min. As the polymer undergoes crystallization, an exothermic peak in the “heat flow versus temperature” trace becomes evident. The peak-temperature of this exotherm is noted as the crystallization temperature or Tmc. A higher Tmc generally means faster crystallization kinetics.

Example 1 Reactive Blend composition with PHA, PBAT, Organic Peroxide and Co-agent

In this example, rheological data for a PHA reactively melt-compounded with PBAT in the presence of an organic peroxide and co-agent is presented. Other additives included in the formulations were EMFORCE BIO™ calcium carbonate (Specialty Minerals), the plasticizer CITROFLEX™ A4 (Vertellus Specialties Inc.); a Slip/antiblock Master Batch which was a mixture composed of 15% by wt. Erucamide (Croda), 15% by wt. OPTIBLOC^(TM) 10 talc filler (Specialty Minerals); a nucleating agent master batch (Nuc. MB) which was composed of cyanuric acid compounded at 33% by wt. into a base PHA resin of 3-hydroxybutanoic acid and 4-hydroxybutanoic acid and 68% by wt. PHA copolymer blend composed of about 34-38% homo-polymer of 3-hydroxybutanoic acid, and about 22-26% co-polymer of 3-hydroxybutanoic acid and 4-hydroxybutanoic acid, where the 4-hydroxybutanoic acid is approximately 10-12 weight percent, and about 38-42% co-polymer of 3-hydroxybutanoic acid and 4-hydroxybutanoic acid with the 4-hydroxybutanoic acid composition being nominally 30 weight percent; peroxide cross linking agent (Akzo Nobel) TRIGONOX™ 117 (tert-butylperoxy 2-ethylhexyl carbonate); co-agent SR444 a blend of pentaerythritol triacrylate and tetratacrylate (Sartomer). The polybutylene-adipate-terephthalate polyester (PBAT) used for blending was Ecoflex (BASF Corp.). The PHA was a blend composed of about 34-38% homo-polymer of 3-hydroxybutanoic acid, and about 22-26% co-polymer of 3-hydroxybutanoic acid and 4-hydroxybutanoic acid, where the 4-hydroxybutanoic acid is approximately 8-14 weight percent, and about 38-42% co-polymer of 3-hydroxybutanoic acid and 4-hydroxybutanoic acid with the 4-hydroxybutanoic acid composition being nominally 25-33 weight percent. The formulation is shown in Table 1 below along with the melt viscosity and melt strength data.

All formulations were compounded using a Leistritz, 27 mm, co-rotating, twin-screw extruder using the following temperatures (from feed to die) 165/164/165/165/167/163/171/168 (° C.), screw speed was 125 rpm and die pressure 2098 psi.

TABLE 1 Composition containing PHA and PBAT reactively blended with peroxide and co-agent. Component (Wt %) 1 PHA BLEND 58.5 PBAT 19.5 CaCO₃ 5 Nuc. MB 3 Slip/antiblock MB 5 Plasticizer 8.75 Peroxide 0.15 Co-agent 0.1 Total (Wt %) 100 Melt Rheology Properties and Melt Crystallization Temperature G′ @ 0.25 rad/s (Pa) 980 η* @ 0.25 rad/s (Pa · s) 8827 Tmc (° C.) 101.9

TABLE 2 Compositions containing PHA and PBSA reactively blended with peroxide and co-agent. Component (Wt %) 1 2 PHA BLEND 79 59 PBSA* 0 20 CaCO₃ 5 5 Nuc. MB 3 3 Slip/antiblock MB 5 5 Plasticizer 7.75 7.75 Peroxide 0.15 0.15 Co-agent* 0.1 0.1 Total (Wt %) 100 100 Melt Rheology Properties and Melt Crystallization Temperature G′ @ 0.25 rad/s (Pa) 549 1413 η* @ 0.25 rad/s (Pa · s) 6975 8749 Tmc (° C.) 105.9 101.8 *PBSA BIONOLLE ™ 3001 (Showa High Polymer Ltd), Co-agent was PE3A, a pentaerythritol type (Sartomer).

The data in Table 1 shows the effects on melt strength and viscosity of a PHA reactive blended with PBAT. To compare these results, Table 2 shows the same formulations (with minor changes in co-agent type and amount of plasticizer) with a pure PHA sample reactively processed and a PHA-polybutylene-succinate-adipate (PBSA) reactive blend. As compared to the reactively processed PHA alone, the PHA-PBAT blend showed higher melt strength (79% higher) and viscosity (27% higher) . However the PHA-PBAT reactive blend had somewhat lower melt strength but comparable viscosity as the PHA-PBSA reactive blend. It was also observed that the addition of PBAT or PBSA lowered the melt crystallization temperature of the PHA by a similar amount. This data shows that reactive blending PHA with other aliphatic or aliphatic-aromatic biodegradable polyesters improves the melt properties which are important when processing these materials for film applications.

Soil Biodegradation Test Method

The biodegradation rate of the subject films was characterized and quantified using a soil burial test. In this test, a small piece of the film specimen (˜5 cm by 9 cm) was buried under 1-2 inches of soil in a plastic container inside a room where the temperature was maintained between 20-25C. The soil was a top soil obtained from a local commercial vegetable farm in Massachusetts. The soil moisture content was maintained by watering regularly (7 grams of water was added to about 100 grams of soil once every three days). Since the container was not covered, the moisture content in the soil dropped from about 9-10% to 1-2% in three days. The buried film specimens are retrieved on a weekly basis (different specimen for each week of elapsed time buried in soil); the retrieved specimens are first washed with water to remove dirt and then dried with paper towels. The dried film specimens (or fragments, if considerable biodegradation had already occurred) are weighed. The measured weight loss quantifies the rate of biodegradation for the different formulations. In the Example presented in this application, the film specimen geometry is kept constant; consequently, the absolute value of the weight loss provides an accurate depiction of the biodegradation kinetics. A higher weight loss translates to faster biodegradation.

Example 2 Blown Films Containing Aromatic/Aliphatic Polyester

In this example, blown films were made and tested for biodegradability. The following PHA formulation was made.

TABLE 3 PHA Formulation for Blown Film Ingredient Wt % PHA Blend 78.00 Nuc MB 3.00 CaCO₃ 5.00 Slip Antiblock MB 5.00 CITROFLEX A4 8.73 Peroxide 0.18 PE3A 0.09

The PHA blend was composed of about 34-38% homo-polymer of 3-hydroxybutanoic acid, and about 22-26% co-polymer of 3-hydroxybutanoic acid and 4-hydroxybutanoic acid, where the 4-hydroxybutanoic acid is approximately 8-14 weight percent, and about 38-42% co-polymer of 3-hydroxybutanoic acid and 4-hydroxybutanoic acid with the 4-hydroxybutanoic acid composition being nominally 25-33 weight percent. The nucleating masterbatch (Nuc. MB) was cyanuric acid that had been previously compounded at a rate of 33% (by weight) into a base resin of 3-hydroxybutanoic acid and 4-hydroxybutanoic acid, and pelleted. The slip anti- block masterbatch was a mixture of erucamide (20% by weight) diatomaceous earth (15% by weight) nucleant masterbatch (3% by weight), pelleted into PHA (62% by weight). The peroxide was tert-butylperoxy-2-ethylhexylcarbonate (available from Akzo Nobel as TRIGANOX™ 117). EMFORCE BIO™ (Specialty Minerals) was used for the calcium carbonate filler. The co-agent was PE3A (pentaerythritol triacrylate).

This PHA formulation was then combined with PBAT (polybutylene adipate terephthalate), in ratios of PHA blend as shown.

TABLE 4 Formulations for Blown Film Ingredient 1 2 PHA Formulation 78.00 58.5 PBAT — 19.5

Blown films were made from these formulations and tested by soil burial, the results are shown in the table below.

TABLE 5 Weight Loss of Blown Films Week 2 Week 3 weight weight Film thickness loss thickness loss No. (mm) (g) (mm) (g) 1 PHA Blend monolayer 0.058 0.007 0.063 0.018 film 2 PHA Blend/PBAT 0.080 0.007 0.075 0.012 monolayer film (75/25)

Film 2 showed a slower rate of weight loss relative to the control (film No. 1).

TABLE 5 Weight Loss of Blown Films Made with Antimicrobial Agents Week 2 Week 3 weight weight Film thickness loss thickness loss No. (mm) (g) (mm) (g) 1 PHA Blend monolayer 0.058 0.007 0.063 0.018 film 2 PHA Blend/PBAT 0.080 0.007 0.075 0.012 monolayer film (75/25)

Unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages, such as those for amounts of materials, elemental contents, times and temperatures of reaction, ratios of amounts, and others, in the following portion of the specification and attached claims may be read as if prefaced by the word “about” even though the term “about” may not expressly appear with the value, amount, or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains error necessarily resulting from the standard deviation found in its underlying respective testing measurements. Furthermore, when numerical ranges are set forth herein, these ranges are inclusive of the recited range end points (i.e., end points may be used). When percentages by weight are used herein, the numerical values reported are relative to the total weight.

Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10. The terms “one,” “a,” or “an” as used herein are intended to include “at least one” or “one or more,” unless otherwise indicated.

Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein is used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

All of the features disclosed in this specification may be combined in any combination. Each feature disclosed in this specification may be replaced by an alternative feature serving the same, equivalent, or similar purpose. Thus, unless expressly stated otherwise, each feature disclosed is only an example of a generic series of equivalent or similar features.

From the above description, one skilled in the art can easily ascertain the essential characteristics of the present invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. Thus, other embodiments are also within the scope of the following claims.

While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims. 

1. A method of preparing a branched polymer composition, comprising reacting a PHA and a polybutylene adipate-terephthalate with a branching agent, thereby forming a branched polymer composition of PHA and a polybutylene adipate-terephthalate, wherein the branching agent is selected from: dicumyl peroxide, t-amyl-2-ethylhexyl peroxycarbonate, 1,1-bis-3,3,5-trimethylclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy) hexane, 2,5-bis(t-butylperoxy)-2,5-dimethylhexane, 2,5-dimethyl-di(t-butylperoxy)hexyne-3, di-t-butyl peroxide, benzoyl peroxide, di-t-amyl peroxide, t-butyl cumyl peroxide, n-butyl-4,4-bis(t-butylperoxy)valerate, 1,1-di(t-butylperoxy)-3,3,5-trimethyl-cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 1,1-di(t-amylperoxy)-cyclohexane, 2,2-di(t-butylperoxy)butane, ethyl-3,3-di(t-butylperoxy)butyrate, 2,2-di(t-amylperoxy)propane, ethyl-3,3-di(t-amylperoxy)butyrate, t-butylperoxy-acetate, t-amylperoxyacetate, t-butylperoxybenzoate, t-amylperoxybenzoate, and di-t-butyldiperoxyphthalate.
 2. The method of claim 1, wherein the concentration of polybutylene adipate-terephthalate is between about 15% and 25% of the total polymer composition. 3.-4. (canceled)
 5. The method of claim 1, wherein the composition further comprises a cross-linking agent for reacting with the polymer composition.
 6. -7. (canceled)
 8. The method of claim 5, wherein the cross-linking agent is diallyl phthalate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, diethylene glycol dimethacrylate, bis (2-methacryloxyethyl) phosphate, or combinations thereof
 9. (canceled)
 10. The method of claim 5, wherein the cross-linking agent is an epoxy-functional styrene-acrylic polymer, an epoxy-functional acrylic copolymer, an epoxy-functional polyolefin copolymer, an oligomer comprising a glycidyl group with an epoxy functional side chain, an epoxy-functional poly(ethylene-glycidyl methacrylate-co-methacrylate), or an epoxidized oil or combinations thereof.
 11. The method of claim 1, further comprising a nucleating agent.
 12. The method of claim 1, wherein the amount of PHA in the polymer composition is 5% to 95% by weight of the composition, 20%-60% by weight of the composition or 30%-50% by weight of the composition.
 13. -14. (canceled)
 15. A method of preparing a film comprising a branched polymer composition, comprising reacting a PHA with a branching agent, thereby forming a branched PHA polymer composition reacting a polybutylene adipate-terephthalate with a branching agent, thereby forming a branched polybutylene adipate-terephthalate composition, exposing the branched PHA composition to conditions that cause melting of the PHA, thereby forming a molten branched PHA composition, exposing the branched polybutylene adipate-terephthalate composition to conditions that cause melting of the polybutylene adipate-terephthalate, thereby forming a molten branched a polybutylene adipate-terephthalate composition co-extruding the molten PHA compositions and the molten polybutylene adipate- terephthalate compositions to form a multi-layered film; thereby making a film comprising branched PHA and branched polybutylene adipate-terephthalate.
 16. A method of making an article comprising a branched polymer composition of a PHA and a polybutylene adipate-terephthalate, comprising the steps of: melt-blending a PHA and a polybutylene adipate-terephthalate and a branching agent under conditions that cause melting and branching of the PHA polymer and the polybutylene adipate-terephthalate, thereby forming a molten branched polymer composition; and forming an article from the branched molten polymer composition; thereby making an article comprising branched polymer composition of branched PHA and branched polybutylene adipate-terephthalate, wherein the branching agent is selected from: dicumyl peroxide, t-amyl-2-ethylhexyl peroxycarbonate, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy) hexane, 2,5-bis(t-butylperoxy)-2,5-dimethylhexane, 2,5-dimethyl-di(t-butylperoxy)hexyne-3, di-t-butyl peroxide, benzoyl peroxide, di-t-amyl peroxide, t-butyl cumyl peroxide, n-butyl-4,4-bis(t-butylperoxy)valerate, 1,1-di(t-butylperoxy)-3,3,5-trimethyl-cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 1,1-di(t-amylperoxy)-cyclohexane, 2,2-di(t-butylperoxy)butane, ethyl-3,3-di(t-butylperoxy)butyrate, 2,2-di(t-amylperoxy)propane, ethyl-3,3-di(t-amylperoxy)butyrate, t-butylperoxy-acetate, t-amylperoxyacetate, t-butylperoxybenzoate, t-amylperoxybenzoate, and di-t-butyldiperoxyphthalate.
 17. (canceled)
 18. The method of claim 2, wherein the composition further comprises one or more additives.
 19. The method of claim 16, wherein the composition further comprises a cross-linking agent for reacting with the polymer composition cross-linking agent is diallyl phthalate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, diethylene glycol dimethacrylate, his (2-methacryloxyethyl) phosphate, an epoxy-functional styrene-acrylic polymer, an epoxy-functional acrylic copolymer, an epoxy-functional polyolefin copolymer, an oligomer comprising a glycidyl group with an epoxy functional side chain, an epoxy-functional poly(ethylene-glycidyl methacrylate-co-methacrylate), or an epoxidized oil or combinations thereof
 20. -30. (canceled)
 31. The method of claim 1, wherein the polyhydroxyalkanoate polymer is a poly(3-hydroxybutyrate) homopolymer, a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with 5% to 15% 4-hydroxybutyrate content, a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with 5% to 22% 3-hydroxyvalerate content, a poly(3-hydroxybutyrate-co-5-hydroxyvalerate) with 5% to 15% 5-hydroxyvalerate content, or a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with 3% to 15% 3-hydroxyhexanoate content.
 32. (canceled)
 33. The method of claim 1, wherein the polyhydroxyalkanoate polymer is a) a poly(3-hydroxybutyrate) homopolymer blended with b) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 5% to 15% 4-hydroxybutyrate content; a) a poly(3-hydroxybutyrate) homopolymer blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22% 3-hydroxyvalerate content; a) a poly(3-hydroxybutyrate) homopolymer blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15% 3-hydroxyhexanoate content; a) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 5% to 15% 4-hydroxybutyrate content blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22% 3-hydroxyvalerate content; a) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with 5% to 15% 4-hydroxybutyrate content blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15% 3-hydroxyhexanoate content or a) a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22% 3-hydroxyvalerate content blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15% 3-hydroxyhexanoate content.
 34. The method of claim 33, wherein the biologically-produced polyhydroxyalkanoate is a) a poly(3-hydroxybutyrate)homopolymer blended with b) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b); a) a poly(3-hydroxybutyrate) homopolymer blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b); a) a poly(3-hydroxybutyrate)homopolymer blended to with b) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b); a) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b); a) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b); or a) a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b).
 35. The method or 34 of claim 34, wherein the weight of polymer a) is 20% to 60% of the combined weight of polymer a) and polymer b) and the weight of polymer b) is 40% to 80% of the combined weight of polymer a) and polymer b).
 36. The method of claim 1, or the article of any one of claims 38-68, where the polyhydroxyalkanoate polymer is a) poly(3-hydroxybutyrate)homopolymer blended with b) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50% 4-hydroxybutyrate content; a) a poly(3-hydroxybutyrate)homopolymer blended with b) a poly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a 20% to 50% 5-hydroxyvalerate content; a) a poly(3-hydroxybutyrate)homopolymer blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50% 3-hydroxyhexanoate content; a) poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 5% to 15% 4-hydroxybutyrate content blended with b) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50% 4-hydroxybutyrate content; a) poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 5% to 15% 4-hydroxybutyrate content blended with b) a poly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a 20% to 50% 5-hydroxyvalerate content; a) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with 5% to 15% 4-hydroxybutyrate content blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50% 3-hydroxyhexanoate content; a) a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22% 3-hydroxyvalerate content blended with b) poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50% 4-hydroxybutyrate content; a) a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22% 3-hydroxyvalerate content blended with b) a poly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a 20% to 50% 5-hydroxyvalerate content; a) a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22% 3-hydroxyvalerate content blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50% 3-hydroxyhexanoate content; a) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15% 3-hydroxyhexanoate content blended with b) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50% 4- hydroxybutyrate content; a) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15% 3-hydroxyhexanoate content blended with b) a poly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a 20% to 50% 5-hydroxyvalerate; or a) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15% 3-hydroxyhexanoate content blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50% 3-hydroxyhexanoate content.
 37. The method of claim 1, wherein the biologically-produced polyhydroxyalkanoate is a) a poly(3-hydroxybutyrate)homopolymer blended with b) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50% 4-hydroxybutyrate content and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b); a) a poly(3-hydroxybutyrate)homopolymer blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 20% to 50% 5-hydroxyvalerate content and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b); a) a poly(3-hydroxybutyrate)homopolymer blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50% 3-hydroxyhexanoate content and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b); a) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 5% to 15% 4-hydroxybutyrate content blended with b) poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50% 4-hydroxybutyrate content and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b);a) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 5% to 15% 4-hydroxybutyrate content blended with b) poly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a 20% to 50% 5-hydroxyvalerate and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b); a) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 5% to 15% 4-hydroxybutyrate content blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50% 3-hydroxyhexanoate content and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b); a) a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22% 3-hydroxyvalerate content blended with b) poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50% 4-hydroxybutyrate content and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b); a) a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22% 3-hydroxyvalerate content blended with b) a poly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a 20% to 50% 5-hydroxyvalerate and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b); a) a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22% 3-hydroxyvalerate content blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50% 3-hydroxyhexanoate content and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b); a) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15% 3-hydroxyhexanoate content blended with b) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50% 4-hydroxybutyrate content and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b); a) a poly(3-hydroxybutyrate-co-3- hydroxyhexanoate) with a 3% to 15% 3-hydroxyhexanoate content blended with b) a poly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a 20% to 50% 5-hydroxyvalerate and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b); or a) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15% 3-hydroxyhexanoate content blended with b) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50% 3-hydroxyhexanoate content and the weight of polymer a) is 5% to 95% of the combined weight of polymer a) and polymer b).
 38. The method of claim 36, wherein the weight of polymer a) is 20% to 60% of the combined weight of polymer a) and polymer b) and the weight of polymer b is 40% to 80% of the combined weight of polymer a) and polymer b).
 39. The method of claim 38, wherein the biologically-produced polyhydroxyalkanoate is further blended with polymer c) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20% to 50% 4-hydroxybutyrate content; c) a poly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a 20% to 50% 5-hydroxyvalerate content or c) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 5% to 50% 3-hydroxyhexanoate content.
 40. -43. (canceled)
 44. The composition made by the method of claim
 1. 45. An article made by the method of claim
 1. 46. The article of claim 45, wherein the article is a film.
 47. -49. (canceled)
 50. The film of claim 46, wherein the film is a tri-layer film having one middle layer composed substantially of PHA, and two outer layers composed substantially of a branched PHA and branched polybutylene adipate-terephthalate.
 51. The film of claim 46, wherein the film is a tri-layer film having one middle layer composed substantially of a branched PHA and branched polybutylene adipate-terephthalate, and two outer layers composed substantially of PHA.
 52. A method of preparing a branched polymer composition, comprising reacting a PHA and a polybutylene adipate-terephthalate, with a branching agent in the presence of pentaerythritol triacrylate, a nucleating agent, and at least one additive thereby forming a branched polymer composition of PHA and polybutylene adipate-terephthalate. 